The labs of Microsoft Research are home to some of the most intriguing innovations in interactivity and the latest breakthrough—following the likes of its 3-D “Holodesk”—is similarly impressive. While the Kinect, for instance, can detect hand gestures via visual inputs (its built-in camera), researchers have now discovered a way for any computer to have motion-sensing capabilities via sound inputs and outputs.

The system is predicated on the Doppler effect, which correlates changes in sound frequency with physical movement. Here, the computer sends out inaudible sound waves via its speakers and the on-board mic picks up how hand movements change the waves, generating the intended effects on-screen. Listening to music won’t get in the way of the interface.

All in all, it's a pretty big deal--the combination of visual and audio motion-sensing inputs will eventually lead to more robust, responsive interactive interfaces.